1. Field of the Invention
The invention is related to the field of data storage, and in particular, to asynchronous data storage that is geographically diverse.
2. Description of the Prior Art
FIG. 1 illustrates data storage system 100 in an example of the prior art. Data storage system 100 includes customer system 101, Network Attached Storage (NAS) system 102, and local storage system 103. Customer system 101 and NAS system 102 are located at customer premises 104. Customer system 101 transfers data files to NAS system 102 over communication link 111. NAS system 102 transfers the data files to local storage system 103 over communication link 112, where local storage system 103 stores the data files. Customer system 101 and local storage system 103 each maintain a version of the data files, so two versions of the data files are maintained at different locations.
Communication links 111-112 could use various communication protocols, such as Small Computer System Interface (SCSI), Fibre Channel (FC), Internet Protocol (IP), and Ethernet.
NAS system 102 handles the receipt and transfer of files on an individual file-by-file basis in real time. Thus, NAS system 102 provides asynchronous data file transfer by transfer a data file when it is ready for transfer, as opposed to transferring the data file later on in a scheduled block transfer. NAS system 102 determines the file type of each data file, and the transfer of the data file is carried out based on the specific file type of the individual data file.
Customer system 101 executes a database application, such as those supplied by Oracle, IBM, and Microsoft. Both the database application and the file type place a severe latency restriction on data file transfer. This latency restriction effectively restricts the distance between NAS system 102 and local storage system 103 to approximately 20 miles.
Unfortunately, the government may mandate that some data files, such as those containing important financial data, be stored at separate locations that are more than 20 miles apart. Sound business practices also dictate that greater geographic diversity be used to store important data.
FIG. 2 illustrates data storage system 200 in an example of the prior art. Data storage system 200 includes customer system 201, Storage Area Network (SAN) switch 202, and remote storage system 203. Customer system 201 and SAN switch 202 are located at customer premises 204. Customer system 201 transfers blocks of data to SAN switch 202 over communication link 211. Each block of data is an amount of data that typically includes multiple data files. SAN switch 202 transfers the blocks of data to remote storage system 203 over communication link 212, where remote storage system 203 stores the blocks of data. Customer system 201 and remote storage system 203 each maintain a version of the data files, so two versions of the data files are maintained at different locations.
Communication links 211-212 could use various communication protocols, such as Small Computer System Interface (SCSI), Fibre Channel (FC), Internet Protocol (IP), bonded Time Division Multiplex (TDM), and Ethernet. Bonded TDM connections utilize special framing interfaces that provide popular interfaces on the customer side and high-bandwidth communications on the network side over unbundled network elements, such as DS1, DS3, OC3, and OC12 connections.
SAN switch 202 handles the receipt and transfer of data files on a block-by-block basis—which is not real-time. Since SAN switch 202 periodically assembles and transfers blocks of data, SAN switch provides synchronous data storage and not asynchronous data storage. For example, a given data file that is received is not transferred in real-time, but rather, may wait for an hour or more before additional files for the block are received or before its block is scheduled for transfer. Many SAN switches provide scheduled night-time back-up of the day's data files through block transfers.
In addition, SAN switch 202 does not determine the file type of each data file. SAN switch 202 does not transfer the data files based on the specific file type of the individual data file.
Because of SAN switch 202, the distance restriction of data storage system 100 is not present in data storage system 200. Unfortunately, SAN switch 202 can be very expensive. In addition, SAN switch 202 uses block transfers that are synchronous and not on a file-by-file basis in real time.